Copolymers, such as ethylene-acrylic acid (EAA) and ethylene-methacrylic acid (EMAA) copolymers, which are prepared by chain polymerization have been widely used as commodity plastics due their ease of production, inexpensive starting materials, and the tunable bulk morphology of final products. The interplay of hydrogen bonding and polymer crystallinity permits the synthesis of wide variety of materials displaying various bulk properties dependant on acid content and degree of branching. For example, commercial EAA copolymer synthesis, is performed by a radically initiated, high-pressure polymerization, and results in the preparation of statistically functionalized copolymers which meet certain desired material properties. However, because of chain transfer side reactions, uncontrollable polymer branching occurs and, because of the essentially random nature of the copolymerization, the incorporation of acid functionality reside in backbone in a statistical fashion. This statistical polymerization is given in the chemical equation, Equation 1, below.

As the sophistication of applications for polymers evolves, the need for well defined polymer microstructures ensues. For these applications, the methods of polymer synthesis must extend beyond the random placement of repeating units common to most chain growth copolymerizations of vinyl monomers. Vinyl copolymerizations, even when perfectly alternating, have significant restrictions to the number of covalently bonded carbon atoms between specific functionalized carbons, almost always three carbon atoms. The homopolymerization of functionalized dienes can also lead the structures equivalent to the alternating copolymerization of vinyl monomers, shown in Equation 2 below. This was reported for poly(ethylene-alt-methylmethacrylate) in Yokota, K. and Hirabayashi, T. Macromolecules 1981, 14, 1613-1616 which also reported the alternating copolymerization of a vinyl monomer and a diene monomer to give a poly(butadiene-alt-methylmethacrylate) with five carbon atoms between acid functionalized carbons, shown in Equation 3 below.

Ring-opening polymerizations of specifically functionalized cycloalkene monomers also give limited possibilities to the placement of specific units on the resulting chains as the ability to prepare a cyclic monomer becomes very difficult and usually prohibitively expensive when the size of the ring exceeds seven or eight atoms.
To overcome such limitations with EAA and EMAA, metathesis polymerization has been applied. The ring opening metathesis copolymerization, ROMP, of a carboxylic acid functionalized cyclooctene with cyclooctene and subsequent hydrogenation of the double bounds of the polymer formed upon olefin metathesis has been reported in Lehman, S. E. and Wagener K. B. ADMET Polymerization. In Handbook of Metathesis, Grubbs, R. H., Ed. Wiley-VCH: 2003; Vol. 3, pp 283-353. The successful preparation of copolymers between 2-10 mol % was achieved by the copolymerization and subsequent hydrogenation of an acid functionalized cyclooctene, as shown in Equation 4 below. These materials were isolated as high-melting, semicrystalline solids, as expected, affording strictly linear materials exhibiting varying levels of crystallinity dependent on comonomer incorporation. Although these polymers did not have the methyl groups and other branched alkyl groups and a statistical amount of acid functionalized carbons in the backbone separated by only one methylene unit, typical of commercially produced EAA and EMAA copolymers, the properties were essentially identical due to the random incorporation of cyclooctene and acid functionalized cyclooctene units.

The acyclic diene metathesis polymerization, ADMET, of a free acid diene has been reported in Schwendeman, J. E. and Wagener K. B. Macromolecules 2004, 37, 4031-4037 as indicated in Equation 5, below. In this polymerization the exothermic ring-opening which occurs with cyclooctene copolymerization is not involved and the polymerization proceeded at a very low rate permitting the competitive deactivation of the metathesis catalyst by the acid groups in the polymerization mixture, which under normal polymerization conditions for ADMET only low molecular weight oligomers resulted. Only by periodic addition of metathesis catalyst to the polymerization mixture was a high molecular weight polymer possible. These polymers displayed very different properties to that of random copolymers, with a low Tm, 13° C., and essentially no Tg while random copolymers displayed much higher Tm values. Unfortunately, the use of these higher levels of catalyst is undesirable when considering the cost to prepare, the difficulties of removing the catalyst, and the limitations imposed on the applications when relatively large amounts of catalyst are left in the polymer.

The polymerization of methyl ester functional polyethylene is also reported in Schwendeman et al. In this case high molecular weight polymer is formed under normal ADMET conditions. Although, in principle, conversion of the ester to an acid functional group is possible, in practice the hydrolysis of an ester in the resulting polymer does not proceed to a large extent. Therefore, a practical route to prepare a periodic, semi-periodic and semi-random poly(ethylene-co-acrylic acid) and poly(ethylene-co-methacrylic acid) remains.